ATP standard wheel sizes:   349 (16 x 1 3/8)   406 (20 x 1.75)   520 (24 x 1 1/8)   559 (26 x 1.5)
Photos courtesy Jonathan Garcia of http://www.rosecityrecumbentcycles.com/. Tire and rim measurements are complicated because there are real measurements, nominal measurements and slang or abbreviated terms that are different in European vs. Asian vs. US. The best reference for ordering tires is the ISO system. Sizes such as 406, 451, 507, 559, 571, 622. That number along with a width number preceding it such as 28-622 printed in small letters on the sidewalls will avoid confusion for shops and consumers when ordering! 451�s are part of the 20� �family� along with the more common 406 (BMX size). The smaller 24� (Also a BMX size) is 507 and the larger is 520. 520 is what the first year Saber had in stock form. In the photo below the left to right "ambiguous sizes" are: 16 x 1.5�, 16 x 1 3/8�, 17 x 1 1/4�, 20 x 1.75�, 20 x 1 1/8�, 24 x 1 1/8�, 26 x 1.5�, 650c, 650b (27.5�), 700c. For more on sizing see https://www.sheldonbrown.com/tire-sizing.html.

	Left to right: 305 (16 x 1.5�), 349 (16 x 1 3/8�), 369 (17 x 1 1/4�), 406 (20 x 1.75�). 349 is the standard 16" front, and 406 is the standard 20" front tire size for the R40.
	Left to right: 406 (20 x 1.75�), 451 (20 x 1 1/8�), 520 (24 x 1 1/8�). 520 is what the year 2000 Saber had in stock form.
	Left to Right: 451 (20 x 1 1/8�), 520 (24 x 1 1/8�). Brakes won�t reach if you wanted to swap these sizes.
	Left to Right: 559 (26 x 1.5�), 571 (650c). These two sizes are usually interchangeable even with rim brakes. The 1995 R40 rear tire was a Specialized Fat Boy 26 x 1.25 (44-559). In 1996 this was widened to 26 x 1.50, and then to 26 x 1.75 in 1997.
	Left to Right: 584 (650b (27.5�)), 622 (700c). Very close in diameter when tires are carefully chosen. Sometimes interchangeable on the same platform if there are tire clearances and disc brake preferred.